Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session F31: Superconductivity: Spectroscopy of Cuprates |
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Sponsoring Units: DCMP Room: 331 |
Tuesday, March 15, 2016 11:15AM - 11:27AM |
F31.00001: Ultrafast Gap Dynamics in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$ Studied by High Resolution trARPES Stephen Parham, Haoxiang Li, Justin Waugh, Xiaoqing Zhou, Thomas Nummy, Justin Griffith, Z. Xu, J. Schneeloch, R.D. Zhong, Genda Gu, Daniel Dessau We perform time and angle resolved photoemission spectroscopy on optimally doped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$ (BSCCO-2212) using higher energy resolution than previously reported. This technique allows us to observe quasiparticle and gap dynamics directly in the time domain. We find that the quasiparticle decays have a rich momentum and energy dependence, with the general trend of faster decays closer to the antinode and faster decays inside the superconducting gap scale. We can understand this entire landscape by modeling the electrons as following a non-equilibrium, ``pseudo''-temperature that controls all electrons in the zone. Using this model, which has zero free parameters, we find excellent agreement with the data. [Preview Abstract] |
Tuesday, March 15, 2016 11:27AM - 11:39AM |
F31.00002: A Tight Binding Approach to Understanding the Orbital Character of Pb-BSSCO and its Effects on Photoemission Matrix Elements Thomas Nummy, Yue Cao, Justin Waugh, Stephen Parham, Haoxiang Li, Xiaoquing Zhou, Sung-Kwan Mo, A. Magrez, H. Berger, Daniel Dessau We measure the near Fermi energy electronic structure of Pb-BSCCO using Angle Resolved Photoemission Spectroscopy (ARPES) for various light polarization, incident at a glancing angle. A strong dependence of the photocurrent for a given crystal momentum on the polarization of light is observed. A minimal model tight binding calculation in a basis of local atomic orbitals is then utilized to determine the orbital composition of the single particle wavefunction as a function of crystal momentum in a single CuO2 plane. Building off of these results, we simulate the relative ARPES photocurrent throughout crystal momentum space in the dipole approximation and compare to our experimental data. These comparisons confirm the presence of changing wavefunction orbital composition throughout the Brillouin zone in Pb-BSCCO. [Preview Abstract] |
Tuesday, March 15, 2016 11:39AM - 11:51AM |
F31.00003: Phonon modes in cuprates possibly related to the 10 meV ARPES kink Adrian Merritt, Seung-Ryong Park, John-Paul Castellan, Genda Gu, Dmitry Reznik One of the possible mechanisms of high Tc superconductivity is Cooper pairing with the help of bosons responsible for kinks in electronic dispersion observed by angle-resolved photoemission (ARPES). Up to now most effort has been devoted to the kinks near 70 meV. More recent ARPES experiments revealed an additional energy scale near 10 meV. Since no magnetic excitations peaked at these energies have been identified, the likeliest candidates appear to be phonons. We recently performed measurements of low-energy phonons in a large single crystal sample of optimally-doped 2212 BSCCO. We measured all phonons below 15 meV. There are many branches, in particular an optic branch disperses from 7 meV from the zone center with an anticrossing with an acoustic branch near h$=$0.2. In addition, there is evidence for a very low energy branch dispersing through 3-4 meV. I will present these results as well as similar data on LSCO and YBCO. A comparison with recent ultrafast optics experiment detecting lattice modes around 10 meV will also be made. [Preview Abstract] |
Tuesday, March 15, 2016 11:51AM - 12:03PM |
F31.00004: Power Law Liquid -- A Unified Form of Low-Energy Nodal Electronic Interactions in Hole Doped Cuprate Superconductors Daniel Dessau, Ted Reber, Xiaoqing Zhou, Nick Plumb, Stephen Parham, Justin Waugh, Yue Cao, Zhe Sun, Haoxiang Li, Qiang Wang, J.S. Wen, Z.J. Xu, Genda Gu, Y. Yoshida, Hiroshi Eiaski, Gerald Arnold Based upon detailed ARPES measurements of Bi2Sr2CaCu2O8$+\delta $ over a wide range of doping levels, we present a new unifying phenomenology for the non-Fermi liquid normal-state interactions (scattering rates) in the nodal direction. This new phenomenology has a continuously varying power law exponent (hence named a Power Law Liquid or PLL), which with doping varies smoothly from a quadratic Fermi Liquid to a linear Marginal Fermi Liquid and beyond. Using the extracted PLL parameters we can calculate the optics and resistivity over a wide range of doping and normal-state temperature values, with the results closely matching the experimental curves. This agreement includes the presence of the T* ``pseudogap'' temperature scale observed in the resistivity curves including the apparent quantum critical point. [Preview Abstract] |
Tuesday, March 15, 2016 12:03PM - 12:15PM |
F31.00005: ARPES Study of Triple Layer Nickelate R$_{4}$Ni$_{3}$O$_{10}$ (R=Pr, La) Haoxiang Li, Xiaoqing Zhou, Thomas Nummy, Junjie Zhang, Victor Pardo, Warren E. Pickett, John F. Mitchell, Daniel S. Dessau Layered nickelates present a similar crystal and electronic structure to the high-T$_c$ cuprates. They are potential candidates to host superconductivity, and have demonstrated intriguing anomalies in resistivity, magnetic susceptibility, and specific heat [1-3]. Here we present an ARPES study of the triple layer nickelate R$_{4}$Ni$_{3}$O$_{10}$ (R=Pr, La) and compare it with density functional calculations. A large hole pocket centered at the zone corners similar to the cuprates is observed, with additional zone folding due to the structural/magnetic cell doubling. An additional band-like feature is found near the Fermi surface at the gamma point, and shows a different symmetry than that of the hole pocket. These details of the fermiology and their relevance to the properties of these materials will be discussed. [1] Z. Zhang et al. J. Solid State Chem. 117, 236 (1995). [2] M. D. Carvalho et al. J. Appl. Phys. 88, 544 (2000). [3] M. Zinkevich et al. J. Alloys Compd. 438, 92 (2007). [Preview Abstract] |
Tuesday, March 15, 2016 12:15PM - 12:27PM |
F31.00006: ABSTRACT WITHDRAWN |
Tuesday, March 15, 2016 12:27PM - 12:39PM |
F31.00007: Photodoping of Effects in Underdoped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ Revealed by Time and Angle Resolved Photoemission Spectroscopy Jonathan Rameau, S. Freutel, I. Avigo, M. Ligges, L. Rettig, P. Zhou, J. Schneeloch, R. Zhong, Z. Xu, Genda Gu, Peter Johnson, Uwe Bovensiepen While in the last several years great strides have been made in the use of ultrafast optical excitation to induce non-equilibrium effects in the superconducting state of cuprate high $T_{c}$ superconductors, less attention has been paid to what such pump-probe experiments might reveal about the equilibrium properties of these materials, particularly in their normal states. Recently we have investigated the non-equilibrium properties of the normal state of optimally doped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ ($T_{c}$ = 91 K) using time and angle resolved photoelectron spectroscopy (tr-ARPES). This effort revealed a pump-induced modification of the nodal mass renormalization at 70 meV as well as a longer-lived photodoping effect. Building on this work, we will present further findings related to the photodoping effect as it is manifested in the normal state of underdoped ($T_{c}$ = 50 K) Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$. [Preview Abstract] |
Tuesday, March 15, 2016 12:39PM - 12:51PM |
F31.00008: The self-energies and bosonic spectrum of high Tc cuprate from laser-based ARPES. Jin Mo Bok, Jong Ju Bae, Han-Yong Choi, Li Yu, X. J. Zhou, Chandra M. Varma While phonon mediated conventional superconductors are revealed by comparing tunneling and neutron scattering experiment, high Tc cuprate which has d-wave symmetry is still in debate. Laser-based AREPS can provide both momentum and energy dependence of spectral function that enables self-energy extraction using one particle Green’s function. It is well known that anisotropy of electronic structure and d-wave superconducting gap on ARPES experiments. We analyzed high resolution APRES data of under and overdoped Bi2212 and extracted both normal and pairing self-energy. Here we report the extracted normal and pairing self-energy in supercondcuting state. Also we obtained bosonic spectrum from both self-energies by performing maximum entropy method. Implications of these results for understanding the superconductivity mechanism will be discussed. [Preview Abstract] |
Tuesday, March 15, 2016 12:51PM - 1:03PM |
F31.00009: Photoinduced Chemical Potential Shifts in Bi2212 Tristan Miller, Christopher Smallwood, Wentao Zhang, Hiroshi Eisaki, Joseph Orenstein, Alessandra Lanzara In superconducting materials, the chemical potential is particularly important because it is the energy of the superconducting condensate. The chemical potential may be perturbed by laser pulses, giving us new insight into the equilibrium properties of cuprate superconductors. Here, we report on studies of the photoinduced change of chemical potential in Bi2212 using time- and angle-resolved photoemission spectroscopy. We make an important distinction between the chemical potential relative to the vacuum energy, and relative to the valence band energy. The observations can be explained with considerations of the density of states. Measurements on different dopings of Bi2212 also provide new clues to the pseudogap phase. [Preview Abstract] |
Tuesday, March 15, 2016 1:03PM - 1:15PM |
F31.00010: Quasi-particles ultrafastly releasing kink bosons to form Fermi arcs in a cuprate superconductor Y. Ishida, T. Saitoh, T. Mochiku, T. Nakane, K. Hirata, S. Shin In a conventional framework, superconductivity is lost at a critical temperature ($T_{c})$ because, at higher temperatures, gluing bosons can no longer bind two electrons into a Cooper pair. In high $T_{c}$ cuprates, it is still unknown how superconductivity vanishes at $T_{c}$. Recent angle-resolved photoemission (ARPES) studies revealed a remnant feature of the $d$-wave superconducting gap in the so-called Fermi arc occurring at $T$ \textgreater $T_{c}$; The loss of superconductivity is thereby attributed to the filling of the near-nodal gap due to spectral broadenings as opposed to the closure of the gap at $T_{c}$ [Reber \textit{et al}., PRB2013; Kondo \textit{et al}., Nature Phys. 2015]. The next step would be to elucidate the underlying mechanism of the spectral broadenings that cause the unconventional loss of superconductivity. We provide evidence that the so-called \textless \textasciitilde 70-meV kink bosons that dress the quasi-particle excitations are playing the key role. We performed time-resolved ARPES on Bi2212 and monitored the responses of the superconducting gap and dressed quasi-particles to a light pulse. We observe an ultrafast loss of superconducting gap near the $d$-wave node, or light-induced Fermi arcs, which is accompanied by spectral broadenings and weight redistributions occurring within the kink binding energy. We discuss that the spectral broadening that induce the Fermi arc is due to the undressing of quasi-particles from the kink bosons. The loss mechanism is beyond the conventional framework, and can accept the unconventional phenomena such as the signatures of Cooper pairs remaining at $T$ \textgreater $T_{c}$. [Preview Abstract] |
Tuesday, March 15, 2016 1:15PM - 1:27PM |
F31.00011: Superconducting Gap and Pseudogap in Heavily Underdoped Bi2212 Cheng Hu, Lin Zhao, Shaolong He, Guodong Liu, Li Yu, Chuangtian Chen, Zuyan Xu, Genda Gu, Xingjiang Zhou The relationship between the pseudogap and superconducting gap in high temperature cuprate superconductors remains an outstanding issue. In this talk, we will present laser-based angle-resolved photoemission spectroscopy results on underdoped Bi2Sr2(Ca,Dy)Cu2O8 high temperature superconductor. The latest generation of ARPES system equipped with the narrow-bandwidth VUV laser and the time-of-flight (TOF) electron energy analyzer is utilized here, which enables us to have super-high energy resolution, high momentum resolution, and simultaneous coverage of two-dimensional momentum space. From detailed temperature dependence near the nodal and antinodal regions, we will discuss the relationship between the pseudogap and superconducting gap in the underdoped cuprate superconductors. [Preview Abstract] |
Tuesday, March 15, 2016 1:27PM - 1:39PM |
F31.00012: Interplay of low-energy bosonic collective modes with incipient charge order in Bi-2212 characterized by momentum-resolved electron energy loss spectroscopy Sean Vig, Anshul Kogar, Vivek Mishra, Melinda Rak, Ali Husain, Genda Gu, Mike Norman, Peter Abbamonte Classifying the collective electronic dynamics of materials is critical to addressing the high temperature superconductivity problem and understanding related collective phenomena. Most current probes are unable to measure the full energy and momentum dependence of the dynamic charge susceptibility in these strongly correlated materials at the meV energy scale relevant to superconductivity. We use our momentum-resolved electron energy loss spectroscopy (M-EELS) technique to perform this measurement, characterizing both the static charge density and the bosonic electronic excitations in the cuprate superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi-2212). I present our measurement of a low temperature diffuse charge ordered state at optimal doping which modulates the observed dispersionless low energy collective excitations. Performing a one-loop correction to the bare electron dispersion, we show these modes reproduce the self-energy anomaly, or ``kink'', as measured by ARPES. I discuss the nature of the charge dynamics that we measured with our technique and its relation to the superconducting state. [Preview Abstract] |
Tuesday, March 15, 2016 1:39PM - 1:51PM |
F31.00013: Resonant inelastic x-ray scattering as a band structure probe of high-temperature superconductors Marton Kanasz-Nagy, Yifei Shi, Israel Klich, Eugene Demler I will analyze recent resonant inelastic x-ray scattering (RIXS) experimental data on $\rm{YBa_2Cu_3O_{6+x}}$ [Minola et al., Phys. Rev. Lett. $\bf 114$, 217003 (2015)] within quasi-particle theory. This measurement has been performed with the incoming photon energy detuned at several values from the resonance maximum, and, surprisingly, the data shows much weaker dependence on detuning than expected from recent measurements on a different cuprate superconductor, $\rm{Bi_2Sr_2CuO_{6+x}}$ [Guarise et al., Nat. Commun. $\bf 5$, 5760 (2014)]. I will demonstrate, that this discrepancy, originally attributed to collective magnetic excitations, can be understood in terms of the differences between the band structures of these materials. We found good agreement between theory and experiment over a large range of dopings [M. Kanasz-Nagy et al., arXiv:1508.06639]. Moreover, I will demonstrate that the RIXS signal depends sensitively on excitations at energies well above the Fermi surface, that are inaccessible to traditionally used band structure probes, such as angle-resolved photoemission spectroscopy. This makes RIXS a powerful probe of band structure, not suffering from surface preparation problems and small sample sizes, making it potentially applicable to a wide range of materials. [Preview Abstract] |
Tuesday, March 15, 2016 1:51PM - 2:03PM |
F31.00014: Doping dependent charge correlation in electron-doped cuprates. Eduardo Da Silva Neto, F. Boschini, M. Zonno, G. A. Sawatzky, A. Damascelli, M. Minola, M. Bluschke, M. Le Tacon, B. Keimer, B. Wu, Y. Li, G. Yu, M. Greven, J. Higgins, Y. Jiang, R. L. Greene, R. Sutarto, F. He, E. Schierle, E. Weschke We use resonant x-ray scattering to measure the charge order in electron-doped high-Tc superconductors and its relationship to antiferromagnetism and superconductivity. First, we establish the presence of charge order in a second family of electron-doped cuprates, LCCO thin films, with similar characteristics to previous observations in NCCO [1]. Second, doping and temperature dependent measurements of NCCO single crystals show that charge order is present in the x $=$ 0.059 to 0.166 doping range, and its doping-dependent wavevector is consistent with the separation between the hot spots on the Fermi surface. For NCCO samples near optimal doping (x $=$ 0.14) the charge order remains constant through the superconducting transition temperature and we find that magnetic fields up to 6 T have a negligible effect on its intensity. The implications of our data to the connections of charge order to antiferromagnetism and superconductivity will be discussed. [1] E. H. da Silva Neto, et al. Science 347, 282 (2015). [Preview Abstract] |
Tuesday, March 15, 2016 2:03PM - 2:15PM |
F31.00015: Resonant Soft X-ray Scattering studies of charge orders in high-temperature cuperates with Transition Edge Sensors Yizhi Fang, Peter Abbamonte, Fanny Rodolakis, Jessica McChesney, Hideyuki Tatsuno, Young Il Joe, Joe Fowler, Kelsey Morgan, William Doriese, Daniel Swetz, Joel Ullom Resonant Soft X-ray studies of high $T_c$ cuperates have implied a complex yet unresolved relationship between charge orders, anitferromagnetism and superconductivity. Unfortunately, at resonance the inelastic florescence background makes it hard to distinguish weak charge orders. To eliminate this issue, we have developed an energy-resolving detector comprised of 240-pixels superconducting Transition-Edge Sensor microcalorimeters. These superconducting sensors obtain exquisite resolution by exploiting the superconducting-to-normal transition to transduce photon energy to temperature and by operating at cryogenic temperatures ($\sim$ 100 mK) where thermal noise is minimal. Initial commissioning was accomplished at Advanced Photon Source Sector 29 in August 2015 and have demonstrated 1.0 eV resolution below 1 keV with efficiency (solid angle $\times$ quantum efficiency) $\sim$ 50 times than that of grating spectrometers. An experiment to study charge orders in LBCO, LESCO and YBCO as a function of doping will take place in November 2015. [Preview Abstract] |
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